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This is Hacker Public Radio episode 3,775 for Friday the 20th of January 2023.

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Today's show is entitled, Emergency Show Posted in 2014, how to make a punch card computer.

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It is hosted by Mike Reng and is about 14 minutes long.

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It carries a clean flag.

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The summary is, how to make a punch card computer from stuff from the kitchen.

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Hi everybody, we're really short of shows at the moment, so I've had to take this one

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out of the reserve queue.

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If you have shows, can you please send them in?

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Because HPR is a project will cease to exist if we don't continue to get shows from

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listeners like you.

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Hello, welcome to Hacker Public Radio.

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My name is Mike Ray.

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You're hearing that sound because this is an emergency show.

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HPR is running low on scheduled podcasts.

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If you would like to submit a show, email admin at HackerPublicRadio.org for more information.

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This is something I've had in my head for decades.

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I can vaguely remember when I was very small, making one of these punch card computers.

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It may have been me or may have been my older brother.

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And I think we probably made it in response to seeing it on the TV or reading it in a book

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or something.

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I have this vague recollection of a serial box with some of my mum's knitting needles sticking

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through the box and putting out the needles and card dropping out at the bottom.

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Now, we're not going to use knitting needles, but we're going to update it a bit.

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I've not done it since I was probably over 40 years ago, but it's just something I've

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remembered for years.

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So what you will need, the main body of the computer consists of an empty breakfast

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serial box.

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Of any sort of average size, or just a normal breakfast serial size box, the first thing

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to do is to cut off the flaps at the top of the box, where the box has been opened

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and the serial has been removed.

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Throw the flaps away except for one of the long flaps from the long side of the box.

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We're going to use that on that made coming handy as a template when we get a little bit

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further on down what we're going to do.

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The other thing we're going to need is some cards about the same width as the box, and

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these can be made from another serial box, sliced up.

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An empty box of the same sort of size will yield about four cards, possibly six if you

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make them not very deep from top to bottom.

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Another thing you need is some bamboo skewers, these are the things that are going to take the place of the knitting needles, in the example I was talking about, from when I was very young, Richard Storman was studying short trousers.

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You're going to need some scissors and or a sharp craft knife, possibly some glue, preferably

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a heavy eye or something washable, and optionally some sticky tape.

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So what you do, the first thing we're going to do is to make a shoot, a sort of shoot at the bottom of the box, now the box, when it's used as computer, it's going to stand on the table.

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And it's bottom, the way it would stand normally, and we're going to cut a flap out of the bottom and stick it back as a shoot and now we do this by making a horizontal cut across the box, about four inches.

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That tends to be just also above the bottom, so it's horizontal cut all the way across, and then we're going to cut down the front edges of the box, from that horizontal cut down to the bottom of the box.

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Now this will form a flap that you can fold out by sticking hand in the top of the box and pushing outwards.

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Now when you're done that, you need to make a fold in that flap, about a centimeter or half an inch from the front edge of the flap, which came away from the horizontal slot that you cut across the box.

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Then you push the new coat that the inside of that flap between the fold and the edge with glue, and then you push it back into the box until the glued part of that flap is against the back wall of the box, and then use some sticky tape to stick it down while the glue dries.

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If you can imagine what that forms is a kind of shoot at the bottom, if you drop something into the top of the box now, it will hit the shoot and slide out the hole in the front where the shoot was cut away from.

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Now take the long flap that you cut from the top of the box and draw a horizontal line across it across the wide length of it, about halfway down, so that you're effectively dividing the flap into two halves along its length.

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And here's where we need to do some rest of the check. You're going to mark out eight or perhaps even 16 points along the line, equally distant, so if you've got eight, if it's an eight bit computer, you've got eight points, so there are nine gaps between the points.

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Measure the width as a flap, mark off the points with a ruler, and then stick that to one side.

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Now we're going to punch some holes in the box at near the top, near the opening, and we're going to do this by holding the template flat that we've just made at the top, against the box, and punching through with a bamboo barbecue skewer,

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or something sharp, or perhaps a knitting needle, if such things still exist, to make the holes in the box, to take the needle, to take the bamboo skewers, and we're going to do the same on the other side, because the bamboo skewers are going to pass all the way through the box from front to back, and they need to be quite accurately inserted, so that each skewer is the same distance from the top of the box.

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The same distance between the tenets and its neighbors, and so the skewers are nice and parallel.

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So once you've done that, if you imagine you've done eight holes, and you've inserted eight skewers, you've got eight parallel skewers passing all the way through the box, a bit like a magic trick, where a man sticks a sword through a wardrobe with a beautiful blonde inside it.

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So now we've made the body as a computer with the eight or 16 or nine or 10, we can make a nine-bit computer skewers through the box, we're going to make the cards.

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Now we need to make, if we've got an eight-bit computer, that's got eight skewers through it, we're going to need to make eight cards.

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These cards need to be almost as wide as the box, but not quite, so that they fit nice and snug, but with no friction in the top of the box.

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The depth of them needs perhaps about four or five inches, 10 or 12 centimeters from top to bottom, big enough to write some stuff on, but not deep enough to be visible through the hole at the bottom where you cut the flat for the shoot.

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Along the long edge of each card, you're going to measure and make some holes that we need our template again for this.

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It's simply to use to make the holes for the skewers, we're going to hold against each card and punch some holes.

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Again, probably starting with using a bamboo skewer, but the holes need to be bigger than the diameter of the skewer, perhaps about five millimeters or a quarter of an inch or so in diameter.

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It's nice and wide so that the skewer passes easily through the holes. A single hole handheld hole punch is good for this, but it's not absolutely necessary. It doesn't matter if the holes are square, as long as the hole is bigger than the actual skewer.

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Then the holes line up where the skewers are. Once you've made eight of those cards, take each card in turn and convert seven out of the eight holes into slots by slicing from the side of the hole to the top of the card.

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You actually remove a little piece of card between the hole and the top edge so you've now got, with each card you've now got one hole and seven slots and for card zero, the left hand hole, if it's a little Indian, is still a hole and the rest of the slots.

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The next card, the first one will be a slot, the next one will be a hole and the remaining six are slots. So you can probably see where I'm going with this, you do it with each card and in each in turn, holes zero to seven become, that remain as holes and the rest become slots.

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So now we've made our cards, we need some data to put on the cards. It would help if you've got eight children at this point because if you've got eight children, you need never forget their birthdays ever again.

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So write a piece of data on each card and write something on the box next to the hole which corresponds to the intact hole on the card.

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Once you've written all the data, then put the cards together in a stack and put them into the top of the box, hold them with one hand and then insert the skewers through the holes and the slots, through the front of the computer and out the back.

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So when you stand it up on its bottom end, what you've got is a cereal box with a nice slippery show to the bottom where something can come out.

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Eight skewers through the top of the box in a line and eight punched cards suspended in the top of the box, but of course each card has got seven slots and one hole, each in a different position.

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Each card is only held in position and prevented from falling by one skewer. So if you now pull out one of the skewers, the card which corresponds to that skewer should drop out the bottom.

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If you have eight children and a third one was called Bobby, pull out Bobby's skewer and Bobby's card will drop out the bottom with his birthday on it and that is a punched card computer.

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I know that some people will be saying, well that's not a computer and it's not and it's eight bits and it's only got eight bits of random access memory and the main problem with it is that each time you remove a piece of data by putting out the skewer, that data is not copied.

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You've not got the data out, but it's still in the computer it's just the computer now only contains seven bits of data. So it's not really a computer, but it's fun.

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Like I say, it's one of those things I have, why you back in a dim and distant past, my brain, one of these days I'm going to get round to making another one. Oh, I should do a little bit of trouble shooting information here. If for some reason, when you pull out a skewer, nothing drops through.

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This could be because of a number of reasons, there's too much friction between the cards. Now when you load the cards into the top of the computer, try and sort of spread them out a little bit so they're not all packed closely in together.

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These are the cards that are too wide and there's some friction between the left and right edges of the cards and the side of the dots, or it could be because the slots are not wide enough and are actually producing some friction between the remaining skewers and the side of the slot so that the card is unable to drop down when you pull out its skewer.

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Those are the only things that we can go wrong. It's as simple as that. If you make this, then you really need to get out more and stop wasting your time and everybody else is.

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